In internal combustion engines, turbines, liquid fuel fired furnaces, and the like, liquid fuel is mixed with an oxidising gas stream, for example an air stream. In a conventional fuel/air mixing device such as a carburettor the fuel discharges from a jet or metering bar in a stream which is torn apart into ligaments which progressively break up and contract into droplets of various sizes. During this process vaporisation takes place and the droplets progressively reduce in size the finest vaporising completely. Ideally, all of the liquid droplets would be vaporised and uniformly distributed in the air stream by the time they reach the combustion zone or combustion chamber.
In practice, especially under the varying conditions which internal combustion engines in particular are subjected to, some of the droplets are incompletely vaporised and this has adverse effects on both fuel economy and the cleanliness of the exhaust gases. In most conventional devices such as carburettors complete vaporisation only occurs at some part throttle conditions. Furthermore vaporisation occurs at a substantial distance away from the point of fuel discharge which distance varies with variable fuel demands of the engine. Fuel vaporasation is improved with forced fuel injection systems where the fuel injection nozzle functions to mechanically atomise the fuel at the tip exposed to the air stream. Fuel injection has several advantages over conventional carburettors but suffers from the disadvantages of high manufacturing costs and additional complexity requiring more sophisticated servicing.
The invention seeks to provide a form of vaporising device improved in the above respects.